[App Service] Add support for os-preference to fix #16509

[madsd]

Description
This PR adds support for setting Linux as the initial OS support for ASEv3 to fix #16509. This is not relevant for ASEv3.
It also improves the new functionality of az appservice ase create-inbound-services to allow the Private DNS Zone to be created for Internal ASEv2 as well, and to be able to only create the private endpoint for ASEv3 and skip DNS services (to support custom DNS).

Testing Guide
The --skip-dns will skip the creation of Private DNS Zone and records

az appservice ase create -n <ase-name> -g <resource-group> --subnet <outbound-subnet-name> --vnet-name <vnet-name> --kind ASEv3

az appservice ase create-inbound-services -n <ase-name> -g <resource-group> --subnet <inbound-subnet-name> --vnet-name <vnet-name> --skip-dns

Creating an ASEv2 and creating the private dns components (zone and records)

az appservice ase create -n <ase-name> -g <resource-group> --subnet <outbound-subnet-name> --vnet-name <vnet-name>

az appservice ase create-inbound-services -n <ase-name> -g <resource-group> --subnet <inbound-subnet-name> --vnet-name <vnet-name>

History Notes

[App Service] Add support for os-preference to fix #16509
[App Service] Improve behavior of appservice ase create-inbound-services to allow skipping DNS services and support DNS for ASEv2

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[yonzhan]

App Service

[yungezz]

hi @qwordy could you pls help to review? thanks